Microvascular bleeding remains a major problem following cardiac surgery with cardiopulmonary bypass (CPB) (Nuttall et al, Anesthesiology 94:773-781, discussion 5A-6A (2001), Hall et al, Cardiovasc. Surg. 10:146-153 (2002)), with up to 5% of patients receiving more than a 10 unit perioperative blood transfusion (Woodman and Harker, Blood 76:1680-1697 (1990)). Approximately 4% of patients require reoperation for hemorrhage (Hall et al, Cardiovasc. Surg. 10:146-153 (2002), Woodman and Harker, Blood 76:1680-1697 (1990)) which is associated with increased mortality and morbidity (Unsworth-White et al, Anannls of Thoracic Surgery 59:664-667 (1995)). Current risk stratification based on clinical, procedural, and biological markers (Wahba et al, Journal of Cardiothoracic & Vascular Anesthesia 11:824-827 (1997), Despotis et al, Anesthesia & Analgesia 82:13-21 (1996)) has been only partially successful, failing to account for much of the postoperative blood loss seen even with “low-risk” primary coronary artery bypass (CABG) surgery (Hardy et al, Canadian Journal of Anaesthesia 38:511-517 (1991)). CPB-induced alterations in the hemostatic system are multifactorial, pertaining to excessive activation of coagulation and fibrinolytic pathways with interplay of cellular and soluble hemostatic and inflammatory systems; hypothermia and hemodilution further complicate the situation (Despotis et al, Annals of Thoracic Surgery 72:S1821-1831 (2001)). Coagulopathy following CPB represents one extreme on a continuum of coagulation function, with perioperative prothrombotic outcomes (e.g. coronary graft thrombosis, myocardial infarction, stroke and pulmonary embolism) at the other end of the spectrum (Spiess and Chandler, Best Practice & Research: Clinical Anaesthesiology 15:195-211 (2001)).
Pathophysiologically, the balance between bleeding, normal hemostasis, and thrombosis is markedly influenced by the rate of thrombin formation and platelet activation (Kunicki and Nugent, Vox Sang. 83 (Suppl 1):85-90 (2002), Slaughter et al, Anesthesiology 80:520-526 (1994)). There is recent evidence that genetic variability modulates the activity in each of these mechanistic pathways (Spiess and Chandler, Best Practice & Research: Clinical Anaesthesiology 15:195-211 (2001)). However, little is known of the role of allotypic coagulation, fibrinolytic and platelet-membrane receptor gene variation in predicting bleeding following CABG surgery; the few studies to date focus only on single-gene variants (Donahue et al, Circulation 107 (7):1003-1008 (2003)). Several prothrombotic genetic polymorphisms are known to exist.
The present invention results, at least in part, from studies designed to investigate the impact of multi-locus genetic influences on the incidence and severity of perioperative bleeding after CABG surgery. The invention provides, in one embodiment, a method of identifying patients with prothrombotic gene polymorphisms, which polymorphisms are associated with increased postoperative bleeding.
Acute renal dysfunction, evidenced by rapid decline in glomerular filtration rate and accumulation of nitrogenous waste products (blood urea nitrogen and creatinine), is a major medical problem occurring in 5% of all patients admitted to the hospital and 30% of those admitted to an intensive care unit (Hou et al, Am. J. Med. 74(2):243-248 (1983)). Furthermore, acute renal injury remains a common, serious complication of cardiac surgery (Conlon et al, Nephrol. Dial Transplant. 14(5):1158-1162 (1999)); multiple etiologies for this observation have been proposed including nephrotoxins, atheroembolism, ischemia-reperfusion, and cardiopulmonary bypass (CPB)-induced activation of inflammatory pathways. Renal failure requiring dialysis occurs in up to 5% of cardiac surgery patients; an additional 8-15% have moderate renal injury (e.g., >1.0 mg/dl peak creatinine rise) (Conlon et al, Nephrol. Dial Transplant. 14(5):1158-1162 (1999), Abel et al, J. Thorac. Cardiovasc. Surg. 71(3):323-333 (1976), Corwin et al, J. Thorac. Cardiovasc. Surg. 98(6)):1107-1112 (1989), Andersson et al, Thorac. Cardiovasc. Surg. 41(4):237-241 (1993), Mora-Mangano et al, Ann. Intern. Med. 128 (3):194-203 (1998), Mangos et al, Aust. NZ J. Med. 25(4):284-289 (1995), Ostermann et al, Intensive Care Med. 26(5):565-571 (2000)). Lesser renal injuries are even more common (>50% aortocoronary bypass surgery patients have ≧25% postoperative rise in serum creatinine). In many settings, including cardiac surgery, acute renal failure is independently predictive of the in-hospital mortality rate even after adjustment for comorbidities and other complications (Conlon et al, Nephrol. Dial Transplant. 14(5): 1158-1162 (1999), Levy et al, JAMA 275 (19):1489-1494 (1996), Chertow et al, Am. J. Med. 104 (4):343-348 (1998)); all degrees of renal injury are associated with increased mortality and other adverse outcomes (Stafford-Smith, Chapter 5—In: Newman, ed. 2003 Society of Cardiovascular Anesthesiologists Monograph—Perioperative Organ Protection: Lippincott Williams & Wilkins, pgs. 89-124 (2003)). Unfortunately, typical characteristics (e.g., advanced age, history of atherosclerotic vascular disease) of those presenting for cardiac surgery make them generally a group at high “renal risk” (Conlon et al, Nephrol. Dial Transplant. 14(5):1158-1162 (1999), Greenberg et al, Am. J. Kidney Dis. 29(3):334-344 (1997), Porter, Miner Electrolyte Metab. 20(4):232-243 (1994), Novis et al, Anesth. Analg. 78(1):143-149 (1994)).
Paradoxically, although the kidneys receive more blood flow per gram of tissue than any other major organ, they are also the most vulnerable to ischemic injury. Metabolic demands from active tubular reabsorption and the oxygen diffusion shunt characteristic of renal circulation contribute to the precarious physiology of renal perfusion including low medullary pO2 (10-20 mmHg) (Brezis and Rosen, N. Engl. J. Med. 332 (10):647-655 (1995)). Key to regulation of renal blood flow are paracrine systems (e.g., renin-angiotensin system [RAS], nitric oxide[NO]) that modulate microvascular function and oxygen delivery in the renal medulla (Navar et al, Physiol. Rev. 76(2):425-536 (1996)). The inflammatory response to CPB generates cytokines (e.g., tumor necrosis factor alpha [TNFα], interleukin 6 [IL-6]) both systemically and locally in the kidney (Cunningham et al, J. Immunol. 168 (11):5817-5823 (2002), Segerer et al, J. Am. Soc. Nephro. 11(1):152-176 (2000)), that have major effects on the renal microcirculation and may lead to tubular injury (Heyman et al, Exp. Nephrol. 8 (4-5):266-274 (2000)). Recent evidence suggests that heritable differences modulate the activation of these pathways.
Although many preoperative predictors have been identified (these are similar to factors predictive of chronic renal dysfunction), risk stratification based on clinical, intraoperative, and biological markers explains only a small part of the variability in postoperative renal dysfunction ((Conlon et al, Nephrol. Dial Transplant. 14(5):1158-1162 (1999), Abel et al, J. Thorac. Cardiovasc. Surg. 71(3):323-333 (1976), Corwin et al, J. Thorac. Cardiovasc. Surg. 98(6)):1107-1112 (1989), Andersson et al, Thorac. Cardiovasc. Surg. 41(4):237-241 (1993), Mora-Mangano et al, Ann. Intern. Med. 128 (3):194-203 (1998), Mangos et al, Aust. NZ J. Med. 25(4):284-289 (1995), Ostermann et al, Intensive Care Med. 26(5):565-571 (2000), Novis et al, Anesth. Analg. 78(1):143-149 (1994), Zanardo et al, J. Thorac. Cardiovasc. Surg. 107 (6):1489-1495 (1994), Yeh et al, J. Thor. Cardiovasc. Surg. 47:79-95 (1964), Porter et al, J. Thorac Cardiovasc. Surg. 53(1):145-152 (1967), McLeish et al, Surg. Gynecol. Obstet. 145 (1):28-32 (1977), Llopart et al, Ren, Fail. 19(2):319-323 (1997), Hilberman et al, J. Thorac. Cardiovasc. Surg. 77(6):880-888 (1979), Heikkinen et al, Ann. Chir. Cynaecol. 75(5):203-209 (1985), Gailiunas et al, J. Thorac. Cardiovasc. Surg. 79(2):241-243 (1980), Doberneck et al, J. Thor. Cardiovasc. Surg. 43:441-452 (1962), Bhat et al, Ann. Intern. Med. 84(6):677-682 (1976)). However, little is known regarding the relationship of the several known polymorphisms associated with altered activation of renal paracrine and/or inflammatory pathways, with acute renal injury following aortocoronary bypass graft (CABG) surgery. The few existing studies have focused on only 2 genetic polymorphisms (Apolipoprotein E [ApoE] T448C(ε4), interleukin 6 [IL6] G-174C) (Chew et al, Anesthesiology 93(2):325-331 (2000), Mackensen et al, Ann. Thor. Surg. (in press) (2004), Gaudino et al, J. Thorac. Cardiovasc. Surg. 126 (4):1107-1112 (2003)) and do not take into account other important pathways/proteins or interactions between potentially synergistic insults.
The present invention further results, at least in part, from studies designed to investigate the association between genetic variants of inflammatory and paracrine pathways at multiple loci and susceptibility to perioperative acute renal injury.
Despite advances in the field of cardiac surgery, significant neurologic morbidity continues to occur (Wolman et al, Stroke 30(3):514-522 (1999), Roach et al, N. Engl. J. Med. 335 (25):185701863 (1996), Newman et al, N. Engl. J. Med. 344:395-402 (2001), Bucerius et al, Ann. Thorac. Surg. 75(2):472-478 (2003)). Indeed, over the past several decades, many technologic advancements in surgery, anesthesia, and the conduct of cardiopulmonary bypass (CPB), coupled with an improved understanding of the pathophysiology of neurologic injury, have allowed surgery to be performed on an increasingly elderly and high-risk group of patients (Ferguson et al, Ann. Thorac. Surg. 73(2):480-489, discussion 9-90 (2002)). Stroke, although less frequent than more subtle types of cerebral injury (such as cognitive dysfunction) (Newman et al, N. Engl. J. Med. 344:395-402 (2001)) remains a significant and debilitating complication of cardiac surgery (Roach et al, N. Engl. J. Med. 335 (25):185701863 (1996)). In addition to being a devastating injury to the patient, diminishing quality of life and increasing mortality, stroke following cardiac surgery also incurs a substantial cost in terms of health-care resource utilization (Roach et al, N. Engl. J. Med. 335 (25):185701863 (1996)). Despite many years of study to understand factors associated with postoperative stroke, questions exist regarding its pathophysiology, and as a result, the ability to understand who is at risk is far from complete.
The variable incidence of stroke after cardiac surgery is thought to be influenced both by patient and procedural risk factors (Borger et al, Eur. J. Cardiothorac. Surg. 19(5):627-632 (2001)). While many of the procedural risk factors have been incorporated in stroke risk indices from observational studies (Newman et al, Circulation 94(9 Suppl):II74-II80 (1996)), they provide incomplete information regarding the full risks of stroke. These risk-indices and associated factors do not include information regarding the genetic makeup of the patient, raising the possibility that heterogeneity seen in the clinical presentation of stroke (both in incidence and severity) may partly reflect underlying genotype.
The pathophysiology of stroke in non-surgical settings is thought to involve complex interactions between pathways associated with coagulation, inflammation, lipid metabolism, apoptosis, and direct cellular injury. Within each of these broad etiologic pathways, genetic variants have been identified. As a result, identification of specific genetic variants involved in stroke can be thought of in mechanistic terms. Although not exclusively so, it appears that pro-inflammatory and pro-thrombotic genes may play a significant role in the etiology and outcome after stroke in non-operative settings. Recently, polymorphisms involving cyclooxygenase-2 (Cipollone et al, JAMA 291 (18):2221-2228 (2004)), apolipoprotein (APOE) (McCarron et al, Stroke 29(9):1882-1887 (1998)), myeloperoxidase (Hoy et al, Atherosclerosis 167 (2):223-230 (2003)), interleukin 6 (IL6) (Greisenegger et al, Thromb. Res. 110 (4):181-186 (2003), Pola et al, Stroke 34(4):881-885 (2003)), intercellular adhesion molecule-1 (ICAM1) (Pola et al, Stroke 34(4):881-885 (2003)), vascular cell adhesion molecule-1 (VCAM1) (Adams et al, BMC Med. Genet. 4 (1):6 (2003)), C-reactive protein (CRP) (Rost et al, Stroke 32(11):2575-2579 (2001), Curb et al, Circulation 107(15):2016-2020 (2003), Ford and Giles, Arterioscler. Thromb. Vasc. Biol. 20(4):1052-1056 (2000)), and various prothrombotic genes (Kahn, Sourth Med. J. 96(4):350-353 (2003), Endler and Mannhalter, Clin., Chim. Acta 330(1-2):31-55 (2003)) have all been examined in studies demonstrating variable relationships to stroke.
The present invention additionally results, at least in part, from studies designed to examine a group of genetic polymorphisms for their potential may influence on perioperative stroke risk (McCarron et al, Stroke 29(9):1882-1887 (1998), Greisenegger et al, Thromb. Res. 110 (4):181-186 (2003), Pola et al, Stroke 34(4):881-885 (2003), Rost et al, Stroke 32(11):2575-2579 (2001), Curb et al, Circulation 107(15):2016-2020 (2003), Ford and Giles, Arterioscler. Thromb. Vasc. Biol. 20(4):1052-1056 (2000), Kahn, Sourth Med. J. 96(4):350-353 (2003), Endler and Mannhalter, Clin., Chim. Acta 330(1-2):31-55 (2003), Meschia et al, BMC Neurol. 3 (1):4 (2003)). These studies have resulted in the identification of specific genetic polymorphisms that modulate the risk of stroke following surgery.